Biomarker record in the Korea Gap (Ulleung Basin) of the southwestern East Sea since the last glacial period

The East Sea, located on the northwest continental margin of the Pacific Ocean, acts an important marine environment sensitive to the global/regional climate change including the East Asian monsoon. GDGT (glycerol dialkyl glycerol tetraether), one of the membrane lipids originated from archaea or bacteria, has been broadly used as a ubiquitous biomarker for the paleoceanogprahic reconstruction. Although the numerous paleoceanographic results in the East Sea have been reported, the GDGT records and its application to the East Sea paleoceanography are still limited. Here we carried out a study of GDGT, testing the applicability of GDGT-derived proxies as a paleoenvironmental indicator and reconstructing the paleoenvironment using a sediment core from the Korea Gap (Ulleung Basin) in the southwestern East Sea. Downcore profiles of GDGT-derived proxies are clearly distinguished in terms of lithology and age, particularly before and after deglaciation. Concerning the seawater temperature reconstruction, the GDGT-derived temperature (TEX86L-temp) change (5~17°C) is larger than alkenone-derived temperature (UK'37-temp) change (11~21°C). Such a different variation between two temperature proxies potentially indicates that they represent the seawater temperature of different water depths. Especially, the TEX86L-temp during the last glacial period was clearly different from the UK'37-temp. The rapid change of TEX86L-temp before and after deglaciation, similar to GDGT[2]/[3], raises the possibility that, in addition to seawater temperature, other factors related to the sea level change may affect TEX86L-temp. Our results suggest that GDGT biomarker record in the Ulleung Basin (southwestern East Sea) is linked to the regional and global change, providing the possible application to reconstruct the paleoenvironmental changes in the East Sea, although care should be taken when interpreting the seawater temperature signal.